5/0 CHARACTERS OF SIMIIDAK existing genera, Cebus, Mycetes, and Callitlirix, now living in South America, are also known in a fossil state. The extinct genus Homunculus is known from the Tertiary strata of Patagonia, and an apparently allied form is Antliropops. These creatures, how- ever, are at present far from exhaustively known. Fam. 2. Simiidae.—The Anthropoid, or Man-like Apes/ may be separated from the lower Apes as a group, Simiae, or perhaps better, on account of the after all slender points of difference, a family Simiidae, which has the following distinctive characters. Though arboreal creatures for the most part, these Apes, when they come to the ground, progress in at least a semi-erect fashion. Moreover, when they, as is usually the case, put their hands upon the ground to aid in walking, they do not rest as do the lower Apes upon the flat of the hand, but upon the back of the fingers. ISTone of the Anthropoids has a tail, or cheek pouches. Ischial callosities are only seen in the Gibbons. There is commonly a laryngeal pouch, which is of large size, and aids in the production of the generally loud voice of these creatures. The hair is rather more scanty than in the Cercopithecidae, which is an approach to Man. The placenta differs in detail from that of the lower Apes, and is exactly like that of Man. These Apes show as farther differences from the underlying Cercopithecidae, the greater length of the arms as compared with the legs, and the presence of a vermiform appendix to the caecum. In the latter but not the former character they agree with Man, whom we shall place in a separate family, Hominidae. The Anthropoid Apes are entirely Old World and intratropical in range at the present time. The Gibbons, genus Hylobates, stand quite at the base of the series of existing Anthropoid Apes. They are the smallest and the most purely tree-frequenting of all the members of that group. Connected with this habit is the structural peculiarity that their arms are proportionately longer than in the other Anthropoids. The affinity of the Gibbons to the Catarrhines is proved by the presence of distinct but smail ischial callosities. Tfce arms are so long that when walking upright the hands reach the ground. The hallux is well developed. The ribs are pairs. In the skull the chief noteworthy character as 1 See the books quoted on p. 576 (footnote).